I have figured out a relative cause of this issue and how I fixed it with me. Many people here have suggested it is materials related AND IT IS. tl;dr Check all blueprints for invalid nodes that have invalid material references (probably a material you were recently working with) by trying to compile them. UE5 wont tell you theres a compilation error (in this case) if the blueprint isnt pulled up. Dont just refresh the node. Delete it and make a new one.
I was following a tutorial for how to drag and drop in-game, and got to the end and everything was working great. I thought I would stop for the night so I closed UE5. I accidently clicked that I didnt want to save changes that I made to a material I was using for Drag and Drop. After that, my UE5 froze while trying to save. Stuck at 75%. When I tried to load back up the game, I had to go way back in the tutorial because the whole drag and drop system was broken. It was saying my DD blueprint was invalid. I kept trying to refresh the node and it made the blueprint appear like it compiled successfully but every time I went to save it would freeze at 50%. But when I Deleted the node for the DD blueprint, everything worked great!! I made a brand new node for the DD and it still worked perfect. If I didnt have the Blueprint pulled up that had the issue with the DD blueprint, then UE5 never told me anything was wrong. But the moment I pulled up the BP that used the DD blueprint, it refused to let me compile because of the issue with the DD blueprint nodes. At it’s core the fix occured because the reference to the material was corrected. It was trying to save an invalid reference to the material which was causing it to freeze!